function[f] = compactdiffcaboct(V,h2);
% function to generate values of f using compact difference scheme
% calling sequence 
% [f] = compactdiffcaboct(V,h2)
% define variables
% V1 -- function V1 generated at different points x1 by using function
% h21 -- h1*h1 ( where h is discretization interval ) h1 = 2/(n1-1)
% a -- coeff for boundaries
% b -- coeff for boundaries 
% c -- coefffor boundaries
% d -- coeff for boundaries
% e -- coeff for boundaries 
% alpha -- compact diff coeff
% alpha1 -- compact diff coeff
% A -- coeff forother points
% A1 -- coeff for other points 
% B -- coeff for other points 
% C -- coeff for other points
% f -- R.H.S of equation Ax = B
% N1 -- number of points of space discretization
% ii -- index variable 
% record of revisions 
% date                           Programmer                     Description of changes
% June 1, 2007                      Asha G                            original code
% declare global values 
global N 
pack ('compactdiffcaboct')
alpha = 2/11;
alpha1 = 1/10;
beta = 0;
%  boundaries 
a = (( 11* alpha) + 35)/12;
b = -(( 5* alpha) +26)/3;
c = (alpha+19)/2;
d1 = (alpha -14)/3;
ee = (11-alpha)/12;

%  other points:
A = 12/11;
A1 = (4/3)* (1-(alpha1));
B = 3/11;
C = 0;

f = zeros(1,N);

for ii = 3:(N-2)
f(ii) = (B*(V(ii+2) -2*V(ii) +V(ii-2)))/(4*h2) + (A*(V(ii+1) -2*V(ii) +V(ii-1)))/h2;
endfor

f(1) = (a*V(1))+(b*V(2))+(c*V(3))+(d1*V(4))+(ee*V(5))/h2;
f(N) = (a*V(N)+ b* V(N-1) +c* V(N-2)+ d1*V(N-3) + ee* V(N-4))/h2;
f(2) = (A1*(V(3)-2*V(2) +V(1)))/h2;
f(N-1) = (A1*(V(N)-2*V(N-1) +V(N-2)))/h2;

end % function compactdiffcaboct